Method for producing silicon powder using waste silicon sludge, silicon powder for producing negative electrode material for secondary batteries, and silicon powder production system

Abstract

The present invention relates to a method for producing silicon powder using waste silicon sludge, silicon powder for producing anode materials for secondary batteries, and a system for producing the silicon powder. More specifically, the present invention relates to a method for efficiently producing high-quality silicon powder that can be used as anode materials for energy storage devices, by recovering and upcycling waste silicon sludge generated in the solar power industry and in the production process of semiconductor wafers as a diverted resource, and the silicon powder and the production system used therein.

Description

[Technical field]

[0001] The present invention relates to a method for producing silicon powder using waste silicon sludge, silicon powder for producing anode materials for secondary batteries, and a system for producing the silicon powder. More specifically, the present invention relates to a method for efficiently producing high-quality silicon powder that can be used as anode materials for energy storage devices by recovering and upcycling waste silicon sludge generated in the solar power industry and in the production process of semiconductor wafers as a useful resource, and the silicon powder and the production system used therein. [Background technology]

[0002] Generally, waste silicon sludge generated in the solar power industry and semiconductor wafer manufacturing processes is simply discarded as there is no suitable use for it. The main upcycling methods known so far are to chemically treat the metal components contained in the waste silicon sludge, dry it, and create low-quality silicon blocks for upcycling, or to simply dry it and use it as a raw material for refractory materials.

[0003] However, because the purity of waste silicon sludge can be increased through refinery, various attempts and methods have been proposed to use it in other industries, such as the energy storage industry, rather than just sorting it and upcycling it in the solar power industry.

[0004] Korean Patent No. 10-2261429 proposes a method of removing cutting oil, treating with acid, filtering, and then producing silicon oxide or silicon / carbon composite. However, the process is too complicated for industrialization, and a large amount of waste liquid is generated as a by-product, making mass production difficult.

[0005] Korean Patent Publication No. 10-2021-0058397 discloses a method for manufacturing an active material for negative electrodes for energy storage by dispersing silicon sludge in alcohol, separating it by gravity, mixing and stirring it with a carbon precursor, and spray drying it. Korean Patent Registration No. 10-1650184 discloses a method for manufacturing silicon aggregates by ultrasonic treatment and then recovering silicon particles. However, in these cases, there is a problem that the cost of processes such as heat treatment increases.

[0006] Meanwhile, since diamond cutters, lubricants, and coolants are used to process waste silicon sludge, technology is required to remove the organic components remaining after cutting.In addition, the moisture content of waste silicon sludge discharged in recent years is not constant but is contained in a very wide range, so there is a need to efficiently remove the moisture.

[0007] Therefore, unlike the existing production equipment and process technology, it is necessary to develop a technology that overcomes the above limitations, upcycles waste silicon sludge, and efficiently mass-produces silicon powder that can be used as an anode material for energy storage devices.

[0008] Furthermore, silicon powder recovered from waste silicon sludge and refined may shrink, aggregate, and harden, and may have poor physical properties due to trace amounts of metal and moisture in the silicon powder during long-term storage. As a result, when silicon powder recovered from waste silicon sludge and refined is used to manufacture a negative electrode material for a secondary battery, the silicon powder may have poor dispersibility and may have increased irreversibility due to problems such as volume expansion.

[0009] Therefore, a new solution is required to solve the problems of long-term storage of silicon powder recovered from waste silicon sludge and the deterioration of its physical properties. Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide a method for producing silicon powder using waste silicon sludge, which can efficiently mass-produce high-purity silicon powder from which moisture and other foreign matter such as organic components have been removed so that the silicon powder can be used as a negative electrode material for energy storage devices (e.g., secondary batteries) by upcycling the waste silicon sludge.

[0011] Another object of the present invention is to provide a novel silicon powder which is capable of suppressing the occurrence of powder shrinkage, aggregation and hardening, and whose physical properties do not deteriorate even during long-term storage.

[0012] Furthermore, still another object of the present invention is to provide a silicon powder manufacturing system capable of efficiently mass-producing high-purity silicon powder from which moisture as well as foreign matter such as organic components have been removed so that the silicon powder can be used as a negative electrode material for an energy storage device (e.g., a secondary battery) by upcycling waste silicon sludge.

[0013] The object of the present invention is not limited to the object mentioned above, and other objects and advantages of the present invention not mentioned can be understood from the following description and can be more clearly understood from the embodiments of the present invention. Also, it can be easily understood that the object and advantages of the present invention can be realized by the means and combinations thereof as set forth in the claims. [Means for solving the problem]

[0014] In view of solving the above-mentioned problems, according to one aspect of the present invention, there is provided a method for producing silicon powder, comprising: (a) a step of pulverizing waste silicon sludge supplied as a raw material in an air atmosphere; and (b) a step of drying the pulverized product obtained in the step (a) in an inert gas atmosphere to remove moisture.

[0015] The average particle size of the waste silicon sludge may be more than 0 cm and less than 20 cm. 50 The value may be greater than 0 μm and less than or equal to 50 μm.

[0016] In the above step (a), the separation of moisture and hydrocarbon organic components may be carried out simultaneously with the pulverization.

[0017] The above step (a) may be carried out in a fluidized bed mill.

[0018] The method may further include, prior to the step (a), a step (a') of pre-treating and pulverizing the waste silicon sludge supplied as a raw material.

[0019] The step (b) may be carried out by flash drying, and the flash drying may be carried out using an oxygen-free inert gas.

[0020] The inert gas is argon (Ar) gas and nitrogen (N 2 ) gases.

[0021] When the moisture content is 0 wt% or more and 3 wt% or less based on a total weight of the waste silicon sludge (100 wt%), the step (b) may be performed in a low-temperature airflow manner at a temperature of 20°C or more.

[0022] When the moisture content is more than 3 wt% and not more than 80 wt% based on the total weight of the waste silicon sludge (100 wt%), the step (b) may be performed in a high-temperature airflow manner at a temperature of 60°C or more.

[0023] The silicon powder may have a moisture content of 5% by weight or less and a carbon content of 10% by weight or less, based on a total weight of 100% by weight.

[0024] According to another aspect of the present invention, there can be provided a silicon powder produced by the method for producing a silicon powder according to the aspect of the present invention.

[0025] The silicon powder can be used as a negative electrode material for secondary batteries.

[0026] Next, in order to solve the above problems, a silicon powder according to another aspect of the present invention is a silicon powder obtained from waste sludge generated in the manufacturing process of semiconductors and solar cells, comprising: 50 Value is 0.1 to 2 μm, D 90 It has a particle size distribution with a value of 0.5 to 5 μm.

[0027] Preferably, the silicon powder for producing the secondary battery negative electrode material of the present invention is D 10 Value is 0.01 to 0.5 μm, D 100 It may have a particle size distribution with a value of 1 to 10 μm.

[0028] Furthermore, the silicon powder for manufacturing a secondary battery negative electrode material of the present invention may have a moisture content of less than 2 wt%, a total metal content of less than 2 wt%, and a carbon content of less than 5 wt%, based on a total weight of 100 wt%.

[0029] Next, from the viewpoint of solving the above-mentioned problems, the silicon powder manufacturing system according to the present invention includes a plurality of cases arranged in a longitudinal direction with a hollow formed inside, a tube arranged to pass through the interiors of the plurality of cases and rotatable in a horizontal direction, and a rotary kiln in which a heating means for heating the tube is arranged inside at least one of the plurality of cases.

[0030] Here, the multiple cases may include a first case having a heating means disposed therein for heating the tube, and a second case having no heating means disposed therein, and may include a third case having a cooling means disposed therein for cooling the tube.

[0031] Preferably, the first case may include a 1-1 case equipped with a heating means for heating the tube to a temperature range of 100 to 200°C, a 1-2 case equipped with a heating means for heating the tube to a temperature range of 200 to 500°C, and a 1-3 case equipped with a heating means for heating the tube to a temperature range of 500 to 1000°C.

[0032] Here, the rotary kiln may further include a raw material supplying device that supplies silicon powder raw material and gas to the inside of the tube, and the raw material supplying device may include a raw material input section where silicon powder raw material is input and stored, a raw material transfer section that supplies the silicon powder raw material stored in the raw material input section to the tube, and a gas supplying section that supplies gas to the inside of the tube.

[0033] Preferably, the gas may include an inert gas.

[0034] Moreover, the tube can be operated under any condition by repeatedly rotating forward and backward so as not to discharge the silicon powder raw material therein.

[0035] Additionally, the manufacturing system of the present invention may further include a drying device configured to dry and pulverize the waste silicon sludge.

[0036] Here, the drying and pulverizing device may include a dryer for drying the waste silicon sludge, a rotary pulverizer equipped with a rotary blade for pulverizing the waste silicon sludge, and a fluidized bed pulverizer including a funnel-shaped induction tube having a diameter that narrows from the top to the bottom and pulverizes the waste silicon sludge by the collision of a fluid flow, and preferably, the induction tube may have an inclination angle of 10 to 20 degrees from the top to the bottom.

[0037] The drying and grinding device may further include a cyclone particle separator, a fine particle collector, and a scrubber. Effect of the Invention

[0038] The method for producing silicon powder using waste silicon sludge of the present invention has the advantage that it can efficiently dry waste silicon sludge having various moisture contents and at the same time removes foreign matter such as organic components, thereby efficiently producing high-quality silicon powder that can be used in secondary batteries, in order to solve the problems and limitations of the conventional technology described above.

[0039] Furthermore, the silicon powder of the present invention, that is, the silicon powder for use in a secondary battery negative electrode material of the present invention, has a strictly controlled particle size distribution, and the occurrence of powder shrinkage, aggregation and hardening is suppressed.

[0040] Furthermore, the silicon powder for use as a secondary battery negative electrode material of the present invention does not lose its physical properties even during long-term storage.

[0041] Furthermore, the silicon powder for secondary battery anode material of the present invention has excellent dispersibility without any deterioration in physical properties when used as an anode material, which ensures reliability and reproducibility when used as an anode material.

[0042] In addition, the silicon powder manufacturing system of the present invention has the advantage of being able to efficiently dry waste silicon sludge with various moisture contents in order to solve the problems and limitations of the conventional technology described above, and at the same time, being able to efficiently produce high-quality silicon powder that can be used in secondary batteries by removing foreign matter such as metal components and organic components.

[0043] The above-mentioned effects and specific effects of the present invention will be described in conjunction with the following description of the preferred embodiment of the invention. [Brief description of the drawings]

[0044] [Figure 1] FIG. 1 is a simplified flow diagram of a method for producing silicon powder using waste silicon sludge according to one embodiment of the present invention. [Diagram 2]FIG. 2 is a simplified flow diagram of a method for producing silicon powder using waste silicon sludge according to another embodiment of the present invention. [Diagram 3] 1 is a cross-sectional view showing a simplified view of a rotary kiln included in a system for producing silicon powder according to an embodiment of the present invention. [Figure 4] 1 is a schematic diagram illustrating a drying and grinding device included in a silicon powder manufacturing system according to an embodiment of the present invention; [Diagram 5] 1 is a conceptual diagram illustrating a silicon powder manufacturing system according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] The above-mentioned objects, features and advantages will be described in detail hereinafter, so that a person having ordinary skill in the art to which the present invention pertains can easily implement the technical idea of ​​the present invention.

[0046] In describing the present invention, if a specific description of known techniques relating to the present invention is deemed to obscure the gist of the present invention, the detailed description will be omitted.

[0047] Of the contents not described in this specification, explanations of those that can be sufficiently inferred from a technical standpoint by a person of ordinary skill in this technical field will be omitted.

[0048] As used herein, the singular expression includes the plural expression unless the context clearly indicates otherwise. The terms "comprise," "contain," "have," and the like, as used herein, should not be construed as including all of the various components described in the specification, but should be construed as including some of the components that may not be included or may further include additional components.

[0049] <Method of manufacturing silicon powder> First, a method for producing silicon powder using waste silicon sludge according to an embodiment of the present invention will be described in detail.

[0050] Referring to FIG. 1, the present invention provides a method for producing silicon powder using waste silicon sludge, the method including: (a) pulverizing waste silicon sludge supplied as a raw material in an air atmosphere; and (b) drying the pulverized product of the step (a) in an inert gas atmosphere to remove moisture.

[0051] (a) Stage The waste silicon sludge aggregates in a so-called filter cake state, and aggregates of various sizes are present in a mixed state. In addition, the waste silicon sludge exists in a state containing moisture because it is left outside. If the moisture is not removed, silicon dioxide (SiO 2 ) There is a problem that an oxide film may be formed. Moreover, metal blades such as diamond cutters used for cutting silicon wafers, lubricants used for cutting, and hydrocarbon organic substances such as coolants remain in the waste silicon sludge, so the waste silicon sludge also contains foreign matter including metal components and carbon-based organic components.

[0052] Therefore, in step (a), a process can be carried out in which the solidified particles of the waste silicon sludge supplied as the raw material are separated, and the silicon sludge particles, which are already relatively small, are crushed so as to be further broken down into smaller particles.

[0053] The average particle size of the waste silicon sludge, which is the raw material supplied, may be, for example, in the range of more than 0 cm and not more than 20 cm, for example, in the range of more than 0 cm and not more than 15 cm, or for example, in the range of more than 0 cm and not more than 10 cm, but is not necessarily limited thereto, and may actually be a mixture of various particle sizes and exist in a solidified state.

[0054] The particle size D of the product crushed in the above step (a) 50The value may be in the range of more than 0 μm and not more than 50 μm, for example, more than 0 μm and not more than 30 μm, for example, more than 0 μm and not more than 10 μm, but is not necessarily limited thereto. The powder pulverized in this manner can suppress shrinkage, aggregation, and solidification, and can suppress deterioration of physical properties due to oxidation, etc. that may occur due to trace amounts of hydrocarbons, moisture, etc. that may remain in the silicon powder even during long-term storage.

[0055] D 50 The D value means the particle size value that occupies 50% of the smallest particle size in the particle distribution of the entire powder. 50 The values ​​are based on the values ​​measured by adding 10 to 20% by weight of the sample to be measured to the IPA solvent (based on 100% by weight), treating it with ultrasound for 10 to 30 minutes, and then analyzing it with a particle size analyzer (Cilas).

[0056] The pulverizing device used in step (a) is not particularly limited as long as it can satisfy the above-mentioned average particle size of the pulverized product. However, it is preferable to simultaneously carry out a process of separating foreign matter such as hydrocarbon organic components including moisture during the pulverization.

[0057] For example, in the step (a), it is preferable to use a fluidized bed pulverizer, and in a more specific example, a cyclone device can be used. Specifically, the waste silicon sludge supplied in the step (a) can be broken down into small pieces by passing through a particle-to-particle collision process in the fluidized bed pulverizer along with the high-speed gas, and at this time, the hydrocarbon organic components, moisture, etc. attached to the silicon sludge are separated in the form of fine particles, which results in the advantage that the silicon sludge is broken down and the foreign matter is separated.

[0058] Alternatively, if the silicon sludge particles, which are the raw material supplied, contain an excessive amount of moisture, a high-temperature airflow (e.g., approximately 400°C or less) can be supplied to the pulverizer in the pulverizing process (a) to remove some of the moisture.

[0059] 2 according to an embodiment of the present invention, in order to perform the pulverization process of step (a) more effectively, if the waste silicon sludge supplied as a raw material has excessive clumping or a large amount of sludge with large particle size is present, a step (a') of pre-treating and pulverizing the waste silicon sludge may be further included before step (a). Thus, a total of two pulverization steps including the pre-treating and pulverizing step (a') and the pulverizing step (a) may be performed, or only the pulverizing step (a) may be performed independently, which may be selected according to the particle clump state and particle size state of the waste silicon sludge provided as a raw material.

[0060] For example, the above (a') pre-grinding step can be carried out using a general grinding device, and the average particle size of the result of the pre-grinding may be, for example, in the range of more than 0 cm and not more than 15 cm, for example, in the range of more than 0 cm and not more than 3 cm, or for example, in the range of more than 0 cm and not more than 1 cm, but is not necessarily limited thereto.

[0061] The crushing device used in the step (a') is not particularly limited, but may be, for example, a ball mill, a bead mill, a blade mill, an air mill, a jet mill, a rod mill, a roller mill, a jaw crusher, an impact crusher, a wheel mill, a hammer mill, or the like.

[0062] (b) Stage Step (b) is a drying process carried out under an inert gas atmosphere in order to more effectively remove moisture from the resultant of step (a).

[0063] According to an embodiment of the present invention, in order to quickly dry the moisture, the step (b) may be performed using a hot air flash drying method in which moisture is vaporized and removed using a high-speed flow of high-temperature gas, and the gas supplied in the flash drying method may be an inert gas from which oxygen has been removed in order to prevent further oxidation. Since an inert gas is used in the flash drying method in the present invention, the drying method may be performed under an inert gas atmosphere.

[0064] According to one embodiment of the present invention, the inert gas in step (b) is argon (Ar) gas and nitrogen (N 2 ) gases, for example, nitrogen gas can be used for flash drying.

[0065] The waste silicon sludge is left outside and exists in a moist state, but since waste silicon sludge is used from various photovoltaic industries and numerous factories, the moisture content of the waste silicon sludge is not constant.

[0066] Meanwhile, since the drying process for removing moisture requires the addition of heat energy along with air drying, it is preferable to adjust the drying temperature differently depending on the moisture content of the waste silicon sludge in order to maximize energy efficiency, which has been attracting attention in recent years as an important issue.

[0067] According to an embodiment of the present invention, when the moisture content of the waste silicon sludge is 0% by weight or more and 3% by weight or less based on the total weight of the waste silicon sludge (100% by weight), the step (b) may be performed in a low-temperature airflow manner, and may be, for example, at a temperature of 20° C. or more, for example, at a temperature of 40° C. or more, for example, at a temperature of 60° C. or more, but is not necessarily limited thereto. In addition, since this is a process for removing moisture, the upper limit of the temperature condition of the low-temperature airflow manner is not particularly determined, but from the viewpoint of energy efficiency, in order not to use an excessive heat source, the temperature may be, for example, at a temperature of 200° C. or less, for example, at a temperature of 150° C. or less, for example, at a temperature of 120° C. or less, but is not necessarily limited thereto.

[0068] According to an embodiment of the present invention, when the moisture content of the waste silicon sludge is more than 3 wt% and less than or equal to 80 wt%, based on the total weight of the waste silicon sludge being 100 wt%, the step (b) may be performed using a high-temperature airflow method, and may be at a temperature of, for example, 80° C. or more, for example, 100° C. or more, for example, 200° C. or more, for example, 300° C. or more, but is not limited thereto. In addition, since this is a process for removing moisture, the upper limit of the temperature condition of the high-temperature airflow method is not particularly determined, but from the viewpoint of energy efficiency, in order not to use an excessive heat source, the temperature may be, for example, 500° C. or less, for example, 400° C. or less, for example, 350° C. or less, but is not necessarily limited thereto.

[0069] In the flash drying step (b), a gas may be supplied under normal pressure conditions, and the flow rate of the gas may be adjusted depending on the equipment selected.

[0070] In the method for producing silicon powder of the present invention, the dried powder is further introduced into a hydrogen reduction furnace to carry out hydrogen reduction, thereby removing the silicon oxide coating present on the surface of the silicon powder, thereby further improving the quality of the produced silicon powder.

[0071] The silicon powder manufacturing method of the present invention can be carried out in a single device in which the above steps (a) and (b) are performed consecutively using a silicon powder manufacturing apparatus. For example, the method may be designed to perform a drying step simultaneously with or sequentially to the grinding step in a single device manufactured by attaching a grinding device to the upper end of a cyclone device.

[0072] In the silicon powder obtained through steps (a) and (b) according to the manufacturing method of the present invention, the moisture content may be, for example, 5 wt % or less, for example, 3 wt % or less, for example, 2 wt % or less, and the carbon content may be, for example, 10 wt % or less, for example, 8 wt % or less, for example, 5 wt % or less, based on a total weight of the silicon powder of 100 wt %, thereby exhibiting excellent quality.

[0073] The silicon powder of the present invention can be used as a material for energy storage devices, for example, as a negative electrode material for secondary batteries.

[0074] <Silicon powder> Next, the silicon powder according to another embodiment of the present invention will be described in detail. The silicon powder according to another embodiment of the present invention can be preferably used as a negative electrode material for secondary batteries.

[0075] The silicon powder for the secondary battery negative electrode material of the present invention is a silicon powder obtained from waste sludge generated in the manufacturing process of semiconductors and solar cells, 50 Value is 0.1 to 2 μm, D 90 It has a particle size distribution with a value of 0.5 to 5 μm.

[0076] Here, D 50 Value, D 90 The D values ​​refer to the particle size values ​​that account for 50% and 90% of the particle size in the distribution of the entire powder. 50 Value and D 90 The values ​​can be measured using a Cilas instrument.

[0077] The silicon powder for use as a secondary battery negative electrode material of the present invention is obtained by recovering and refining waste sludge generated during the manufacturing process of semiconductors and solar cells, and has a particularly controlled particle size distribution.

[0078] D of silicon powder for secondary battery negative electrode material of the present invention 50 Values ​​are 0.1 to 2 μm, D 90The particle size is controlled to 0.5 to 5 μm to suppress shrinkage, aggregation, and hardening of the powder, and to suppress deterioration of physical properties that may occur due to trace amounts of metal and moisture in the silicon powder even during long-term storage. Furthermore, the silicon powder for secondary battery negative electrode material having the particle size controlled as described above can ensure reliability and reproducibility when used as a material for secondary battery negative electrode material.

[0079] D of silicon powder for secondary battery negative electrode material of the present invention 50 The value can be controlled to be 0.1 to 2 μm, preferably 0.3 to 1 μm, and more preferably 0.5 to 0.9 μm.

[0080] Furthermore, the D of the silicon powder for the secondary battery negative electrode material of the present invention 90 The value can be controlled to be 0.5 to 5 μm, preferably 0.8 to 4 μm, and more preferably 1 to 3.5 μm.

[0081] As described above, the silicon powder for secondary battery anode materials having a controlled size distribution is prevented from shrinking, agglomerating, and solidifying, and thus the deterioration of physical properties that may occur due to trace amounts of metal and moisture in the silicon powder during long-term storage is prevented. Furthermore, the silicon powder for secondary battery anode materials having a controlled particle size as described above can ensure reliability and reproducibility when used as a material for secondary battery anode materials.

[0082] In addition, preferably, the silicon powder for a secondary battery negative electrode material of the present invention is D 10 Value is 0.01 to 0.5 μm, D 100 It may have a particle size distribution with a value between 1 and 10 μm.

[0083] Furthermore, as described above, the silicon powder for use as a secondary battery negative electrode material of the present invention is obtained from waste sludge generated in the manufacturing process of semiconductors and solar cells, and thus impurities, moisture, and the like contained in the raw materials are removed.

[0084] Accordingly, the silicon powder for use as a secondary battery negative electrode material according to the present invention may preferably have a moisture content of less than 2 wt % based on a total weight of 100 wt % through a moisture removal process, and more preferably, the moisture content may be less than 1 wt %.

[0085] Furthermore, although the silicon powder for use in the secondary battery negative electrode material of the present invention may contain trace amounts of metals such as Al, Fe, and Cu in the ppm range, the silicon powder for use in the secondary battery negative electrode material of the present invention may contain less than 2 wt % of such metal components, and more preferably less than 1 wt %.

[0086] Preferably, the silicon powder of the present invention can be produced by the method for producing silicon powder according to one embodiment of the present invention described above.

[0087] <Silicon powder manufacturing system> Next, a silicon powder manufacturing system according to still another embodiment of the present invention will be described in detail.

[0088] Rotary kiln 3, the silicon powder manufacturing system of the present invention includes a rotary kiln 100. First, the rotary kiln 100 included in the manufacturing system of the present invention will be described in detail.

[0089] Referring to FIG. 3, the silicon powder manufacturing system of the present invention includes a plurality of cases 10 arranged in a longitudinal direction with a hollow formed therein, a tube 20 arranged to pass through the interiors of the plurality of cases 10 and rotatable in a horizontal direction, and a rotary kiln 100 in which a heating means (H) for heating the tube 20 is arranged inside at least one of the plurality of cases 10.

[0090] 3, the plurality of cases 10 are hollow inside and are arranged in the length direction, in other words, in the horizontal direction.

[0091] In FIG. 3, the plurality of cases 10 are shown in a box shape, but the shape of the case 10 is not particularly limited as long as it has a structure that surrounds the tube 20.

[0092] A heating means (H) for heating the tube 20 is disposed inside at least one of the cases 10. Although not limited thereto, the heating means (H) may be formed in a coil shape surrounding the tube as shown in FIG.

[0093] 3, the plurality of cases 10 are arranged in the length direction and can apply heat to the tube 20 in different temperature ranges, respectively, so that the plurality of cases 10 can provide a temperature gradient in the length direction of the tube 20.

[0094] Preferably, the multiple cases 10 may include a first case 11 having a heating means (H) arranged therein for heating the tube 20, and a second case 30 in which no heating means is arranged.

[0095] Here, the first case 11 may include a 1-1 case 12 equipped with a heating means (H) for heating the tube 20 to a temperature range of 100 to 200°C, a 1-2 case 13 equipped with a heating means (H) for heating the tube 20 to a temperature range of 200 to 500°C, and a 1-3 case 14 equipped with a heating means (H) for heating the tube 20 to a temperature range of 500 to 1000°C.

[0096] Thereby, the plurality of cases 10 can provide a temperature gradient of various temperature ranges to the tubes 20 .

[0097] The plurality of cases 10 may further include a third case (not shown) in which a cooling means (not shown) for cooling the tube is disposed. Here, the cooling means may be a device such as a cooling module.

[0098] Next, referring to FIG. 3, the rotary kiln 100 of the present invention includes a tube 20 that is disposed so as to penetrate through the interiors of the multiple cases 10 and is horizontally rotatable.

[0099] The tube 20 may be formed of a hollow cylindrical tube, but the cross section of the tube 20 is not necessarily limited to a circular shape, and may of course have various shapes such as a triangle, a rectangle, and a hexagon.

[0100] The silicon powder raw material moves along the length direction inside the tube 20. The silicon powder can move along the length direction inside the tube 20 by rotating the tube 20. For this reason, a screw-shaped partition may be formed inside the tube 20 to allow the silicon powder to move. The tube 20 may also be disposed at an angle to facilitate the movement of the silicon powder.

[0101] The tube 20 is disposed to penetrate through the interiors of the multiple cases 10. As described above, the multiple cases 10 can provide a temperature gradient of various temperature ranges to the tube 20. Thus, the silicon powder moving along the length direction inside the tube 20 can be heat-treated in various temperature ranges by the heat supplied from the multiple cases.

[0102] Further, referring to FIG. 3, the rotary kiln 100 may further include a raw material supplying device for supplying silicon powder raw material and gas into the inside of the tube 20.

[0103] Preferably, the raw material supplying device may include a raw material input section 41 where silicon powder raw material is input and stored, a raw material transfer section 42 that supplies the silicon powder raw material stored in the raw material input section 41 to the tube 20, and a gas supply section 43 that supplies gas into the inside of the tube.

[0104] Here, the gas may include an inert gas, and the inert gas may be argon (Ar) gas and nitrogen (N 2 ) gases, for example, nitrogen gas can be used.

[0105] Referring to FIG. 3, the silicon powder raw material that has passed through the tube 20 can be discharged from the discharge port 60, and other gases can be separated by the residual gas separator 50.

[0106] In addition, the rotary kiln 100 of the present invention can operate such that the tube 20 repeats forward and reverse rotation under any condition, preventing the silicon powder raw material inside from being discharged.

[0107] Here, the given condition may be, for example, a condition under which a fault signal of the rotary kiln 100 is generated.

[0108] The operation of the tube 20 as described above can be controlled by a control device (not shown) that controls the rotary kiln 100 .

[0109] Drying and grinding equipment Now referring to FIG. 4, the silicon powder production system of the present invention may further include a drying and grinding device 200 configured to dry and grind the waste silicon sludge.

[0110] The drying and crushing device 200 refers to an apparatus configured to dry and crush the waste silicon sludge.

[0111] Referring to FIG. 4, the drying and pulverizing device 200 may include a dryer for drying the waste silicon sludge, a rotary pulverizer having a rotary blade for pulverizing the waste silicon sludge, and a fluidized bed pulverizer including a funnel-shaped guide tube having a diameter that narrows from the top to the bottom and pulverizing the waste silicon sludge by the collision of a fluid flow.

[0112] Here, it is preferable that the lower part of the guide tube has an inclination angle of 10 to 20 degrees with respect to the upper part.

[0113] Additionally, the drying and grinding apparatus 200 may further include a cyclone particle separator, a fine particle collector, and a scrubber.

[0114] The waste silicon sludge is first put into a dryer, which dries the waste silicon sludge with hot air at 200 to 250°C.

[0115] Next, the dried waste silicon sludge is pulverized by the rotary pulverizer and the fluidized bed pulverizer. As described above, the waste silicon sludge is first pulverized by the rotary blades of the rotary pulverizer, and then the waste silicon sludge is pulverized by the fluidized bed pulverizer. At this time, the fluidized bed pulverizer is fed with 25 to 30 m of high-temperature, high-velocity fluid. 3 The high temperature, high velocity fluid may be supplied at a rate of 1000 rpm / hr, and nitrogen gas may be used as the high temperature, high velocity fluid.

[0116] The silicon powder discharged from the fluidized bed mill may pass through the cyclone particle separator, the fine particle collector, and the scrubber in this order.

[0117] As described above, the silicon powder discharged from the fluidized bed mill is separated by the cyclone particle separator and transferred to the fine particle collector. Fine particles that are difficult to collect in the cyclone particle separator are finally collected through a bag filter (not shown), and ultrafine particles that pass through the bag filter are finally collected and discharged in a scrubber.

[0118] At this time, in order to smoothly guide the airflow and crush the silicon particles, it is preferable that the lower part has an inclination angle of 10 to 20 degrees from the upper part, and for example, the inclination angle may be about 15 degrees. The lump silicon moves to the upper part of the funnel-shaped tube together with the flow of the high-temperature nitrogen gas and falls to the lower part, and the gas reaches the lower part while being compressed by a certain volume through the funnel-shaped tube, and the gas speed increases by up to 20% or more compared to the inflow speed, which can act as a driving force for rotating and wearing the lump silicon at high speed.

[0119] The lower part of the fluidized bed mill is configured with a gentle funnel-shaped bottom with an inclination angle based on the ground, and is configured so that large chunks of silicon gather in the center, and the chunks that rain down from the upper part to the lower part can naturally collide with and be crushed by the chunks that gather in the center of the lower part.

[0120] Meanwhile, the filter cake of unseparated lump silicon continues to rotate in the lower part of the fluidized bed mill, undergoing drying, rotation, collision and separation processes until the particles are finally dried and separated.

[0121] However, if too many silicon particles are supplied, the rotation may stop, the particles may accumulate on the bottom, and the flow may be blocked. In consideration of these points, the supply rate of the silicon raw material for drying is preferably, for example, about 70 to 120 kg / hr. If the supply rate of the silicon raw material exceeds 120 kg / hr, the drying quality may deteriorate, and the silicon chunks may not be easily decomposed and crushed. On the other hand, if the supply rate of the raw material is less than 70 kg / hr, the production yield may be low, and mass productivity may decrease.

[0122] 5, Fig. 3 shows a conceptual diagram of a silicon powder manufacturing system according to the present invention. The silicon powder manufacturing system according to the present invention includes the above-mentioned rotary kiln 100, and preferably includes a drying and crushing device 200 for drying and crushing the silicon powder raw material.

[0123] The silicon powder raw material that has passed through the drying and crushing device 200 is transferred to the rotary kiln 100 described above and undergoes heat treatment. The silicon powder raw material that has been heat-treated by the rotary kiln 100 is finally refined so that it can be used as a material for the negative electrode of an energy storage device (e.g., a secondary battery).

[0124] Furthermore, preferably, the silicon powder production system of the present invention can be used in the production method of the present invention described above, and can be used to produce the silicon powder of the present invention described above.

[0125] The present invention will be described in more detail below with reference to preferred embodiments thereof, which are presented as preferred examples of the present invention and are not to be construed as limiting the present invention in any sense.

[0126] <Example> 1. Silicon powder production (1) Example 1 As the feed material, 100 kg of filter cake of silicon powder with a moisture content of 45% by weight was prepared, and crushed at room temperature (23-25°C) at a speed of 30-60 Hz / bead and a feed rate of 3-10 kg / min using a roll mill crushing device (manufacturer: INOX ECO-M Co., Ltd.) equipped with a two-shaft crushing shaft (wet type) and a single-shaft tunnel crushing shaft (wet type).

[0127] The pulverized silicon powder was placed in a cyclone device (manufacturer: INOX ECO-M Co., Ltd.). The drying temperature of the dryer was set to 60° C., and hot air nitrogen stream drying was performed using nitrogen gas for within 5 minutes.

[0128] The properties of the silicon powder thus prepared according to Example 1 are shown in Table 1 below.

[0129] (2) Examples 2 to 3 and Comparative Examples 1 to 3 Silicon powder was produced in the same manner as in Example 1, but silicon powders of Examples 2 and 3 and Comparative Examples 1 to 3 having particle size distributions as shown in Table 1 below were produced.

[0130] [Table 1]

[0131] The particle size distribution of the silicon powder set forth in Table 1 above was measured using a Cilas instrument.

[0132] In addition, the moisture content of the silicon powder was analyzed by measuring the weight change of the sample in a drying oven, the metal content was measured using an ICP-ODS device, and the carbon content was measured using a carbon analyzer (CS995).

[0133] 2. Evaluation of physical properties The dispersion stability of the silicon powders according to the above-mentioned Examples and Comparative Examples was evaluated.

[0134] Using the silicon powders of Examples 1 to 3 and Comparative Examples 1 to 3, respective silicon slurries were produced.

[0135] Specifically, each silicon powder was mixed with NMP to obtain a slurry with a silicon content of 10% by weight, and the resulting slurry was treated with 20 kHz ultrasonic waves at a power of 500 Watts in a continuous circulation manner for 30 minutes to produce silicon slurries using the silicon powders of Examples 1 to 3 and Comparative Examples 1 to 3.

[0136] In order to evaluate the dispersion stability of the silicon slurries, each silicon slurry was stored in a cylinder with perforations, and then observed to see if layer separation occurred over time, and the height excluding the clear upper layer liquid that separated into the upper layer was measured as a % of the initial height. The height excluding the clear upper layer liquid that separated into the upper layer was measured as a % of the initial height, and the results are shown in Table 2 below.

[0137] [Table 2]

[0138] From the above test results, it can be seen that the examples according to the present invention have superior long-term storage stability compared to the comparative examples.

[0139] Therefore, the silicon powder according to the present invention has excellent long-term storage stability, is prevented from deteriorating in physical properties, and can be used for producing anode materials having excellent plasticity.

[0140] Although the present invention has been described above, it is clear that the present invention is not limited to the embodiments disclosed in this specification, and various modifications can be made by those skilled in the art within the scope of the technical concept of the present invention. Furthermore, even if the effects of the configuration of the present invention are not explicitly described and explained while describing the embodiments of the present invention, it is natural that the effects that can be predicted by the configuration should also be recognized. [Explanation of symbols]

[0141] 100 Rotary Kiln 10 Cases 11 Case 1 12 Case 1-1 13 Case 1-2 14 Cases 1-3 20 Tubes 30 Case 2 41 Raw material input section 42 Raw material transfer section 43 Gas Supply Section 50 Residual Gas Separator 60 outlet 200 Drying and grinding equipment

Claims

1. (a) grinding waste silicon sludge provided as a raw material in an air atmosphere; (b) drying the result of the grinding in step (a) under an inert gas atmosphere to remove moisture; Including, A method for producing silicon powder.

2. The average particle size of the waste silicon sludge is more than 0 cm and less than 20 cm; The particle size D of the product pulverized in the above step (a) ５０ The value is greater than 0 μm and less than or equal to 50 μm. The method for producing silicon powder according to claim 1 .

3. In the above step (a), the crushing is performed simultaneously with the separation of moisture and hydrocarbon organic components. The method for producing silicon powder according to claim 1 .

4. The above step (a) is carried out in a fluidized bed mill. The method for producing silicon powder according to claim 1 .

5. Before the step (a), the method further includes a step (a') of pre-treating and crushing the waste silicon sludge provided as a raw material; The method for producing silicon powder according to claim 1 .

6. The above step (b) is carried out by an air flow drying method, The air flow drying method is carried out using an inert gas that does not contain oxygen. The method for producing silicon powder according to claim 1 .

7. The inert gas is argon (Ar) gas and nitrogen (N ２ ) gases, The method for producing silicon powder according to claim 6.

8. When the moisture content is 0 wt% or more and 3 wt% or less based on the total weight of the waste silicon sludge (100 wt%), the step (b) is carried out in a low-temperature airflow manner at a temperature of 20°C or more; The method for producing silicon powder according to claim 1 .

9. When the moisture content is more than 3 wt% and less than 80 wt% based on the total weight of the waste silicon sludge (100 wt%), the step (b) is carried out in a high-temperature airflow manner at a temperature of 60°C or more; The method for producing silicon powder according to claim 1 .

10. The silicon powder has a moisture content of 5 wt% or less and a carbon content of 10 wt% or less, based on a total weight of 100 wt%. The method for producing silicon powder according to claim 1 .

11. A silicon powder obtained from waste sludge generated during the manufacturing process of semiconductors and solar cells, D ５０ Value is 0.1 to 2 μm, D ９０ having a particle size distribution with a value of 0.5 to 5 μm; Silicon powder for manufacturing negative electrode materials for secondary batteries.

12. The silicon powder is D １０ Value is 0.01 to 0.5 μm, D １００ having a particle size distribution with a value of 1 to 10 μm; The silicon powder for producing a secondary battery negative electrode material according to claim 11.

13. Based on 100% total weight, The moisture content is less than 2% by weight. The silicon powder for producing a secondary battery negative electrode material according to claim 11.

14. Based on 100% total weight, The total metal content contained is less than 2% by weight. The silicon powder for producing a secondary battery negative electrode material according to claim 11.

15. Based on 100% total weight, The carbon content is less than 5% by weight. The silicon powder for producing a secondary battery negative electrode material according to claim 11.

16. A plurality of cases arranged in a longitudinal direction, each case having a hollow space formed therein; a tube disposed to pass through the interiors of the plurality of cases and capable of rotating in a horizontal direction; A rotary kiln in which a heating means for heating the tubes is disposed inside at least one of the cases; Including, Silicon powder manufacturing system.

17. The plurality of cases are: a first case having a heating means disposed therein for heating the tube; a second case in which no heating means is disposed; Including, The system for producing silicon powder according to claim 16.

18. The plurality of cases are: a third case having a cooling means disposed therein for cooling the tube; The system for producing silicon powder according to claim 17.

19. The first case is A first case-1 including a heating means for heating the tube to a temperature range of 100 to 200° C.; A first and second case including a heating means for heating the tube to a temperature range of 200 to 500° C.; A first to third case is provided with a heating means for heating the tube to a temperature range of 500 to 1000°C; Including, The system for producing silicon powder according to claim 17.

20. The heating means is A coil formed around the tube, The system for producing silicon powder according to claim 16.

21. The rotary kiln is The method further includes a raw material supply device for supplying silicon powder raw material and gas into the inside of the tube, The raw material supply device is a raw material input section into which silicon powder raw material is input and stored; a raw material transfer unit that supplies the silicon powder raw material stored in the raw material input unit to the tube; a gas supply unit that supplies gas to the inside of the tube; Including, The system for producing silicon powder according to claim 16.

22. The gas comprises an inert gas. The system for producing silicon powder according to claim 21.

23. The tube is Under any conditions, Repeated forward and reverse rotation, It works to prevent the silicon powder raw material inside from being discharged. The system for producing silicon powder according to claim 16.

24. Further comprising a drying and grinding device configured to dry and grind the waste silicon sludge. The system for producing silicon powder according to claim 16.

25. The drying and grinding device comprises: A dryer for drying the waste silicon sludge; a rotary crusher having a rotary blade for crushing the waste silicon sludge; A fluidized bed pulverizer includes a funnel-shaped induction tube whose diameter becomes smaller from the top to the bottom, and pulverizes the waste silicon sludge by the collision of a fluid flow; Including, The system for producing silicon powder according to claim 24.

26. The induction tube is The lower part has an inclination angle of 10 to 20 degrees based on the upper part. The system for producing silicon powder according to claim 25.

27. The drying and grinding device comprises: Further comprising a cyclone particle separator, a fine particle collector, and a scrubber. The system for producing silicon powder according to claim 25.

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